/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.catalina.tribes.io;

import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectStreamClass;
import java.lang.reflect.Modifier;
import java.lang.reflect.Proxy;

/**
 * Custom subclass of <code>ObjectInputStream</code> that loads from the
 * class loader for this web application.  This allows classes defined only
 * with the web application to be found correctly.
 *
 * @author Craig R. McClanahan
 * @author Bip Thelin
 * @author Filip Hanik
 */
public final class ReplicationStream extends ObjectInputStream {

	/**
	 * The class loader we will use to resolve classes.
	 */
	private ClassLoader[] classLoaders = null;

	/**
	 * Construct a new instance of CustomObjectInputStream
	 *
	 * @param stream       The input stream we will read from
	 * @param classLoaders The class loader array used to instantiate objects
	 * @throws IOException if an input/output error occurs
	 */
	public ReplicationStream(InputStream stream,
	                         ClassLoader[] classLoaders)
			throws IOException {

		super(stream);
		this.classLoaders = classLoaders;
	}

	/**
	 * Load the local class equivalent of the specified stream class
	 * description, by using the class loader assigned to this Context.
	 *
	 * @param classDesc Class description from the input stream
	 * @throws ClassNotFoundException if this class cannot be found
	 * @throws IOException            if an input/output error occurs
	 */
	@Override
	public Class<?> resolveClass(ObjectStreamClass classDesc)
			throws ClassNotFoundException, IOException {
		String name = classDesc.getName();
		try {
			return resolveClass(name);
		} catch (ClassNotFoundException e) {
			return super.resolveClass(classDesc);
		}
	}

	public Class<?> resolveClass(String name)
			throws ClassNotFoundException, IOException {

		boolean tryRepFirst = name.startsWith("org.apache.catalina.tribes");
		try {
			if (tryRepFirst)
				return findReplicationClass(name);
			else
				return findExternalClass(name);
		} catch (Exception x) {
			if (tryRepFirst)
				return findExternalClass(name);
			else
				return findReplicationClass(name);
		}
	}

	/**
	 * ObjectInputStream.resolveProxyClass has some funky way of using
	 * the incorrect class loader to resolve proxy classes, let's do it our way instead
	 */
	@Override
	protected Class<?> resolveProxyClass(String[] interfaces)
			throws IOException, ClassNotFoundException {

		ClassLoader latestLoader;
		if (classLoaders != null && classLoaders.length > 0) {
			latestLoader = classLoaders[0];
		} else {
			latestLoader = null;
		}
		ClassLoader nonPublicLoader = null;
		boolean hasNonPublicInterface = false;

		// define proxy in class loader of non-public interface(s), if any
		Class<?>[] classObjs = new Class[interfaces.length];
		for (int i = 0; i < interfaces.length; i++) {
			Class<?> cl = this.resolveClass(interfaces[i]);
			if (latestLoader == null) latestLoader = cl.getClassLoader();
			if ((cl.getModifiers() & Modifier.PUBLIC) == 0) {
				if (hasNonPublicInterface) {
					if (nonPublicLoader != cl.getClassLoader()) {
						throw new IllegalAccessError(
								"conflicting non-public interface class loaders");
					}
				} else {
					nonPublicLoader = cl.getClassLoader();
					hasNonPublicInterface = true;
				}
			}
			classObjs[i] = cl;
		}
		try {
			return Proxy.getProxyClass(hasNonPublicInterface ? nonPublicLoader
					: latestLoader, classObjs);
		} catch (IllegalArgumentException e) {
			throw new ClassNotFoundException(null, e);
		}
	}

	public Class<?> findReplicationClass(String name)
			throws ClassNotFoundException, IOException {
		Class<?> clazz = Class.forName(name, false, getClass().getClassLoader());
		return clazz;
	}

	public Class<?> findExternalClass(String name) throws ClassNotFoundException {
		ClassNotFoundException cnfe = null;
		for (int i = 0; i < classLoaders.length; i++) {
			try {
				Class<?> clazz = Class.forName(name, false, classLoaders[i]);
				return clazz;
			} catch (ClassNotFoundException x) {
				cnfe = x;
			}
		}
		if (cnfe != null) throw cnfe;
		else throw new ClassNotFoundException(name);
	}

	@Override
	public void close() throws IOException {
		this.classLoaders = null;
		super.close();
	}


}
